A file of signals intelligence reports, messages, and correspondence issued by the Government Code and Cypher School and sent by the head ('C') of the Secret Intelligence Service (MI6) to the Prime Minister, Winston Churchill. This file includes the following reports on the Russian Front: from the War Office to Moscow warning the Soviets of an impending German attack on the Orel/Kharkov front and giving the German order of battle for the area, see 3138; a minute from the Chief of the Imperial General Staff (CIGS) to the Prime Minister (PM) with an accompanying map illustrating the area of Operation CITADEL, see 3138; and the PM asked the CIGS for the Soviets' strength in the area.